Liquid laundry detergents have been known in the art for many decades.
Modern detergents are preferably comprised of blends of anionic and nonionic surfactants with any number of ingredients being added in order to improve cleaning performance and reduce the cost of these formulations. In recent times, laundry detergents have undergone significant reduction in levels of surfactants. These formulations with their corresponding low active levels are somewhat ineffective at stain removal. Often enzymes are included in these liquid compositions in order to improve performance. The addition of a chlorine or color-safe bleach added directly to the wash water in the laundry machine as a separate product is needed due to the deficiencies of these products.
For example, U.S. Pat. No. 6,025,316 (Cao et al.) discloses detergent compositions with good performance in the absence of bleach actives. However, although the compositions comprise common synthetic anionic and nonionic surfactants along with fatty acids and polymers, the claimed and preferred compositions comprise enzymes to facilitate the stain removal.
U.S. Pat. No. 6,387,868 (Uno et al.) discloses clear liquid laundry detergent compositions comprising linear alkyl benzene sulfonate, sodium silicate, alkyl ether sulfate, nonionic surfactant, (either alcohol ethoxylate or phenol ethoxylates), metal-chelating agent, pH adjuster, freezing/clouding inhibitor, water and optional components, preferably a fluorosurfactant. The complexity of the formulations is noteworthy, and there is mention in the disclosure of the difficulties in obtaining clear and stable liquid compositions comprising these types of synthetic surfactants and sodium silicate ('868, column 1, lines 46-54), which apparently precipitated the need for the added amide surfactants and other adjuncts to gain freeze/thaw stability.
U.S. Pat. No. 6,451,752 (Delroisse et al.) discloses a method of pre-treating bleachable stains with a composition comprising a transition metal complex that functions as a bleach catalyst, bringing atmospheric oxygen to the stain for bleaching.
US Patent Application Publication US 2006/0166853 (Feyt) describes an approach to increased stain removal in the absence of bleach actives. The inventors describe the use of a fructan derivative, most preferably a carboxyalkylinulin, a dicarboxyinulin, 6-carboxylinulin, or fructan polycarboxylic acid in detergent compositions.
Finally, U.S. Pat. NO. 4,692,275 (Secemski et al.) discloses powdered compositions with linear alkyl benzene sulfonate (LAS), alcohol ether sulfate (AES), silicate, carbonate, polyacrylate and other adjuncts. The inventors teach preferred ratios of sulfonate to sulfate of from about 3.5:1 to about 1.5:1, that is they teach incorporating more sulfonate than sulfate in their compositions. In the highly built laundry powders described in the '275 patent, it is preferable to have LAS>AES such that mixed micelles mitigate the precipitation of the hard water salts of the benzene sulfonate surfactant.
A perusal of the prior art demonstrates a clear need for improved liquid laundry detergent compositions that show enhanced efficacy on bleachable stains yet do not contain any bleach actives or enzymes of any kind. Particularly there is an absence of practical, inexpensive liquid laundry detergent compositions that demonstrate high efficacy and that can bleach stains only through the use of selected combinations of common surfactant and builders.
It has now been surprisingly found that the combination of silicate with polyacrylate and specific anionic and nonionic surfactants produces detergent compositions that exhibit exceptional stain removal capability. Unexpectedly, silicate has been found to be the key to the enhanced bleaching of bleachable stains in the absence of traditional bleach and enzyme actives.